Using Variables

You can use variables to give virtual-server specific values for a class without
having to define each value individually. A variable is defined in the obj.conf file. You can define your own variables, but the user interface
will not recognize them. The variable that is most useful in the user interface
is the variable $id, which represents the ID of the virtual server. Whenever
you enter this variable, the server substitutes the value for the individual
virtual server ID.

There are a few other variables, such as $accesslog (the path to each
virtual server’s access log) and $docroot (the path to each virtual
server’s document root), that you may occasionally see, but $id is the
only one you should need to enter into a field.